Nonvolatile memory device

ABSTRACT

A nonvolatile memory device includes a cell string having a plurality of memory cells connected to one bit line. A page buffer is connected to the bit line via a sensing node and connected to the cell string via the bit line. The page buffer includes a first latch for storing bit line setup information and a second latch for storing forcing information. The first latch is configured to output the bit line setup information to the sensing node, and the second latch is configured to output the forcing information to the sensing node independently of the first latch.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2016-0156059, filed on Nov. 22, 2016, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

BACKGROUND

The disclosure relates to a nonvolatile memory device, and moreparticularly, to a nonvolatile memory device including a page buffer forperforming a programming operation on a memory cell.

A semiconductor memory device is a memory device implemented usingsemiconductors such as silicon (Si), germanium (Ge), gallium arsenide(GaAs), or indium phosphide (InP). A semiconductor memory device may bedivided into a volatile memory device and a nonvolatile memory device.

A nonvolatile memory device is a memory device in which data stored inthe nonvolatile memory device does not disappear even if its powersupply is interrupted. Examples of a nonvolatile memory device areread-only memory (ROM), programmable ROM (PROM), erasable PROM (EPROM),electrically erasable PROM (EEPROM), a flash memory device, phase-changerandom-access memory (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM),or ferroelectric RAM (FRAM). The flash memory device may be divided intoa NOR type and a NAND type.

SUMMARY

The disclosure provides a nonvolatile memory device capable ofperforming a direct forcing operation without performing a dumpingoperation in a program execution process of the nonvolatile memorydevice.

According to an aspect of the disclosure, there is provided anonvolatile memory device, which includes a cell string having aplurality of memory cells connected to a bit line, and a page bufferconnected to the bit line via a sensing node and connected to the cellstring via the bit line. The page buffer includes a first latch forstoring bit line setup information and a second latch for storingforcing information. The first latch is configured to output the bitline setup information to the sensing node, and the second latch isconfigured to output the forcing information to the sensing nodeindependently of the first latch.

According to another aspect of the disclosure, there is provided anonvolatile memory device having a plurality of cell strings, whichinclude a plurality of memory cells, and a page buffer with a shield bitline structure connected to the plurality of cell strings via aplurality of bit lines. The page buffer includes a first path foroutputting bit line setup information to a sensing node and a secondpath, different from the first path, for outputting forcing informationto the sensing node. The first and second paths are independentlyactivated.

According to another aspect of the disclosure, there is provided anonvolatile memory device having a nonvolatile memory and a page buffercircuit. The nonvolatile memory has a plurality of memory-cell strings.Each of the memory-cell strings includes a plurality of memory cellsaddressed by the same bit line and a different one of multiple wordlines, and the memory cells of each of the memory-cell strings areaddressed by a different bit line than the memory cells of every otherof the plurality of memory cell strings. The page buffer circuitincludes a first latch, a second latch, and a switching circuit. Theswitching circuit conveys first data stored by the first latch or seconddata stored by the second latch to a selected memory cell of thenonvolatile memory that is addressed by a selected one of the bit linesand a selected one of the word lines.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is a block diagram of a nonvolatile memory device according to anexample embodiment of the disclosure;

FIG. 2 is a block diagram of a nonvolatile memory device according to anexample embodiment of the disclosure;

FIG. 3 is a circuit diagram of a memory block according to an exampleembodiment of the disclosure;

FIG. 4 is a circuit diagram of another example of a memory block BLK0′included in a memory cell array according to an example embodiment ofthe disclosure;

FIG. 5 is a perspective view of the memory block BLK0′ of FIG. 4;

FIG. 6 is a graph illustrating a threshold voltage distribution ofmemory cells according to an example embodiment of the disclosure;

FIG. 7 is a flowchart illustrating an operation of a nonvolatile memorydevice according to an example embodiment of the disclosure;

FIG. 8 is a flowchart illustrating an operation of a nonvolatile memorydevice according to an example embodiment of the disclosure;

FIG. 9 is a circuit diagram of a nonvolatile memory device according toan example embodiment of the disclosure;

FIG. 10 is a timing diagram of a programming process of a nonvolatilememory device according to an example embodiment of the disclosure;

FIG. 11 is a circuit diagram of a page buffer according to an exampleembodiment of the disclosure;

FIG. 12 is a block diagram of a nonvolatile memory device according toan example embodiment of the disclosure;

FIG. 13 is a circuit diagram of a nonvolatile memory device according toan example embodiment of the disclosure;

FIG. 14 is a timing diagram of a programming process of a nonvolatilememory device according to an example embodiment of the disclosure;

FIG. 15 is a block diagram of a page buffer according to an exampleembodiment of the disclosure; and

FIG. 16 is a block diagram of a computing system device including anonvolatile memory device according to an example embodiment of thedisclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a block diagram of a nonvolatile memory device according to anexample embodiment of the disclosure.

Referring to FIG. 1, a nonvolatile memory device 10 may include a pagebuffer circuit 110, a memory cell array 120, a row decoder 130, and acontrol logic 140. Although the nonvolatile memory device 10 is shown asbeing a flash memory device as an example, it is to be understood thatthe disclosure is not limited to a flash memory device, and may beapplied to any type of nonvolatile memory devices (e.g., read-onlymemory (ROM), programmable ROM (PROM), erasable PROM (EPROM),electrically erasable PROM (EEPROM), a flash memory device, phase-changerandom-access memory (PRAM), magnetic RAM (MRAM), resistive RAM (RRAM),ferroelectric RAM (FRAM), etc.).

The page buffer circuit 110 may operate as a write driver or as a senseamplifier depending on an operation mode. During a programmingoperation, the page buffer circuit 110 may transfer a bit line voltagecorresponding to data to be programmed to a bit line of the memory cellarray 120. During a read operation, the page buffer circuit 110 maysense data stored in a selected memory cell through the bit line. Thepage buffer circuit 110 may latch the sensed data and externally outputthe latched data. In addition, the page buffer circuit 110 may includeone or more page buffers and each of the page buffers may include afirst latch 111 and a second latch 112 that include informationnecessary for a programming operation. According to an exampleembodiment of the disclosure, the first latch 111 may store informationabout a bit line setup operation and the second latch 112 may storeinformation about a forcing operation. Detailed descriptions thereofwill be described later below with reference to FIG. 2 or the like.

The memory cell array 120 may be connected to the row decoder 130 viaword lines WL0 through WLn-1, a cell string selecting line SSL, and aground selecting line GSL. The memory cell array 120 may be connected tothe page buffer circuit 110 via bit lines BL0 through BLm-1. The memorycell array 120 may include a plurality of NAND cell strings. Each of theNAND cell strings may be connected to a bit line via a cell stringselecting transistor SST. The memory cell array 120 may be formed ofplanes including a plurality of memory blocks, and the plurality ofmemory blocks may include a plurality of pages. The plurality of pagesmay include a plurality of memory cells. And each page may include aplurality of memory cells MC0 through MCm-1.

According to an embodiment of the disclosure, a two-dimensional (2D)memory array or a three-dimensional (3D) memory array is provided. The3D memory array is monolithically formed on an active region disposedover a silicon substrate and at least one physical level of memory cellarrays having circuits formed on or in the silicon substrate as circuitsrelated to an operation of memory cells. The term “monolithically”indicates that layers of each level forming the 3D memory array arestacked directly on layers of each lower level of the 3D memory array.

According to an example embodiment of the disclosure, the 3D memoryarray includes vertical NAND cell strings arranged in a verticaldirection such that at least one memory cell is located above anothermemory cell. The at least one memory cell may include a charge traplayer.

U.S. Pat. No. 7,679,133, No. 8,553,466, No. 8,654,587, No. 8,559,235,and U.S. Patent Application Publication No. 2011-0233648 areincorporated herein by reference in their entirety as describingsuitable configurations for a 3D memory array including multiple levelsand in which word lines and/or bit lines are shared between the levels.The memory cell array 120 will be described in detail with reference toFIGS. 3 through 5.

The row decoder 130 may select any one of the memory blocks of thememory cell array 120 in response to an address ADDR. The row decoder130 may select any one of the word lines of the selected memory block.The row decoder 130 may transfer a word line voltage from a voltagegenerator (not shown) to the word line of the selected memory block.

The control logic 140 may receive a programming command CMD and mayoutput various control signals for controlling the page buffer circuit110 and the row decoder 130 to perform a programming operation inresponse to the programming command CMD.

FIG. 2 is a block diagram of a nonvolatile memory device according to anexample embodiment of the disclosure. In FIG. 2, like reference numeralsto those in FIG. 1 denote like elements, and therefore, repeateddescriptions thereof will not be given herein.

Referring to FIGS. 1 and 2, a nonvolatile memory device 20 may include apage buffer 210 and a cell string 220. The page buffer 210 may include afirst latch 211, a second latch 212, a switching circuit 213, and a bitline selecting circuit 214. In addition, the cell string 220 may besubstantially the same as a cell string in the memory cell array 120 ofFIG. 1, which will be described later below with reference to FIG. 3.

The first latch 211 may store information about a bit line setupoperation during a programming operation. In more detail, the firstlatch 211 may include distinct information for distinguishing, from eachother, a cell to be programmed and a cell to be inhibited. During thebit line setup operation, the page buffer 210 may apply differentvoltages to the cell to be programmed and the cell to be inhibited byusing the programming/inhibiting distinct information that is applied toa sensing node SO by the first latch 211.

The second latch 212 may store information about a forcing operationduring a programming operation. In more detail, the second latch 212 mayinclude distinct information for distinguishing, from each other, a cellto be forced and a cell not to be forced. During the forcing operation,the page buffer 210 may apply different voltages to the cell to beforced and the cell not to be forced by using the forcing distinctinformation stored in the second latch 212. In an example embodiment ofthe disclosure, the second latch 212 may directly apply the forcingdistinct information to the sensing node SO under the control of theswitching circuit 213 without a dumping operation for the first latch211, in which the second latch 212 dumps the forcing information to thefirst latch 211 during the forcing operation. Accordingly, when the pagebuffer 210 performs a forcing operation during a programming operationfor the cell string 220, the forcing operation may be performed withoutthe dumping operation for the first latch 211, so that the programperformance may be improved.

The switching circuit 213 may control a connection between the sensingnode SO and the first and second latches 211 and 212. In more detail,the switching circuit 213 may connect the first latch 211 to the sensingnode SO in the bit line setup operation and may connect the second latch212 to the sensing node SO in the forcing operation. Accordingly, thesecond latch 212 including forcing information may be directly connectedto the sensing node SO to apply the forcing information withoutperforming the dumping operation for the first latch 211 through theswitching circuit 213, and the page buffer 210 may perform a forcingoperation on the cell string 220 using the forcing information. To thisend, the switching circuit 213 may include one or more switching devicesfor performing a switching operation.

The bit line selecting circuit 214 may control a connection between abit line and the sensing node SO. To this end, the bit line selectingcircuit 214 may include one or more switching devices for performing aswitching operation. The bit line selection circuit 214 may apply, tothe cell string 220, the programming/inhibiting distinct information orthe forcing information that is applied to the sensing node SO by thefirst latch 211 or the second latch 212. Detailed descriptions thereofwill be described later below with reference to FIG. 10.

FIG. 3 is a circuit diagram of a memory block according to an exampleembodiment of the disclosure.

Referring to FIG. 3, for example, the memory cell array 120 (of FIG. 1)may be a memory cell array of a horizontal NAND flash memory, and mayinclude a plurality of memory blocks. Each memory block BLK11 mayinclude n (n is an integer of 2 or more) cell strings STRs in which aplurality of memory cells MC (e.g., MC1 through MCn) are connected inseries in a direction of bit lines BL0 through BLm-1. FIG. 3 shows anexample in which each cell string STR includes eight memory cells.

A NAND flash memory device having the structure shown in FIG. 3 iserased on a block basis and executes a program in page unitscorresponding to each of the word lines WL0 through WLn. FIG. 3 shows anexample in which n pages for n word lines WL1 through WLn are providedin one block. In addition, the nonvolatile memory device 10 of FIG. 1may include a plurality of memory cell arrays that perform the sameoperation with the same structure as the memory cell array 120 describedabove.

FIG. 4 is a circuit diagram of another example of a memory block BLK0′included in a memory cell array according to an example embodiment ofthe disclosure.

Referring to FIG. 4, for example, the memory cell array 120 (of FIG. 1)may be a memory cell array of a vertical NAND flash memory, and mayinclude a plurality of memory blocks. Each memory block BLK0′ mayinclude a plurality of NAND cell strings NS11 through NS33, a pluralityof word lines WL1 through WL8, a plurality of bit lines BL1 through BL3,a plurality of ground selecting lines GSL1 through GSL3, a plurality ofcell string selecting lines SSL1 through SSL3, and a common source lineCSL. The number of NAND cell strings, the number of word lines, thenumber of bit lines, the number of ground selecting lines, and thenumber of cell string selecting lines may be variously changed accordingto an example embodiment.

The NAND cell strings NS11, NS21 and NS31 are provided between the firstbit line BL1 and the common source line CSL, the NAND cell strings NS12,NS22 and NS32 are provided between the second bit line BL2 and thecommon source line CSL, and the NAND cell strings NS13, NS23 and NS33are provided between the third bit line BL3 and the common source lineCSL. Each NAND cell string (e.g., NS11) may include the cell stringselecting transistor SST, a plurality of memory cells MC1 through MC8,and a ground selecting transistor GST that are connected in series.

Cell strings connected in common to one bit line form one column Forexample, the cell strings NS11, NS21 and NS31 connected in common to thefirst bit line BL1 may correspond to a first column, the cell stringsNS12, NS22 and NS32 connected in common to the second bit line BL2 maycorrespond to a second column, and the cell strings NS13, NS23, NS33connected in common to the third bit line BL3 may correspond to a thirdcolumn.

Cell strings connected to one string selecting line form one row. Forexample, the cell strings NS11, NS12, and NS13 connected to the firstcell string selecting line SSL1 may correspond to a first row, the cellstrings NS21, NS22 and NS23 connected to the second cell stringselecting line SSL2 may correspond to a second row, and the cell stringsNS31, NS32, NS33 connected to the third cell string selecting line SSL3may correspond to a third row.

The cell string selecting transistor SST is connected to a correspondingstring selecting line among the string selecting lines SSL1 throughSSL3. The plurality of memory cells MC1 through MC8 are connected to thecorresponding word lines WL1 to WL8, respectively. The ground selectingtransistor GST is connected to a corresponding ground selecting lineamong the ground selecting lines GSL1 through GSL3. The cell stringselecting transistor SST is connected to a corresponding bit line amongthe bit lines BL1 through BL3, and the ground selecting transistor GSTis connected to the common source line CSL.

Word lines (e.g., WL1) having the same height are commonly connected toeach other. The cell string selecting lines SSL1 through SSL3 areseparated from each other, and the ground selecting lines GSL1 throughGSL3 are also separated from each other. For example, when memory cellsconnected to the first word line WL1 and belonging to the cell stringsNS11, NS12, and NS13 are programmed, the first word line WL1 and thefirst cell string selecting line SSL1 are selected. The ground selectinglines GSL1 through GSL3 may be commonly connected to each other.

FIG. 5 is a perspective view of the memory block BLK0′ of FIG. 4.

Referring to FIG. 5, each memory block included in, e.g., the memorycell array 120 (of FIG. 1), is formed in a direction perpendicular to asubstrate SUB. Although FIG. 5 shows that a memory block includes two ofthe selecting lines GSL and SSL, eight of the word lines WL1 throughWL8, and three of the bit lines BL1 through BL3, in practice it may bemore or less than these.

The substrate SUB has a first conductivity type (e.g., a p-type), and acommon source line CSL extending along a first direction (e.g., a Ydirection) and doped with impurities of a second conductivity type(e.g., an n-type) is provided on the substrate SUB. A plurality ofinsulating layers IL extending along the first direction aresequentially provided along a third direction (e.g., a Z-direction) on aregion of the substrate SUB between two adjacent common source linesCSL, and the plurality of insulating layers IL are spaced apart fromeach other by a specific distance along the third second directions. Forexample, the plurality of insulating layers IL may include an insulatingmaterial such as silicon oxide.

A plurality of pillars P arranged sequentially along the first directionand passing through the plurality of insulating layers IL along thethird direction are provided on the region of the substrate SUB betweenthe two adjacent common source lines CSL. For example, the plurality ofpillars P may penetrate the plurality of insulating layers IL andcontact the substrate SUB. In more detail, a surface layer S of eachpillar P may include a first type of silicon material and may functionas a channel region. An inner layer I of each pillar P may include aninsulating material such as silicon oxide or an air gap.

In the region of the substrate SUB between the two adjacent commonsource lines CSL, a charge storage layer CS is provided along exposedsurfaces of the insulating layers IL, the pillars P, and the substrateSUB. The charge storage layer CS may include a gate insulating layer(referred to as a tunneling insulating layer), a charge trap layer, anda blocking insulating layer. For example, the charge storage layer CSmay have an oxide-nitride-oxide (ONO) structure. In addition, in theregion between the two adjacent common source lines CSL, a gateelectrode GE such as the selecting lines GSL and SSL and the word linesWL1 through WL8 is formed on an exposed surface of the charge storagelayer CS.

Drains or drain contacts DR are provided on the plurality of pillars P,respectively. For example, the drains or drain contacts DR may include asilicon material doped with impurities of a second conductivity type.The bit lines BL1 through BL3 extending in a second direction (e.g., anX-direction) and spaced apart by a certain distance along the firstdirection are provided on the drains DR.

FIG. 6 is a graph illustrating threshold voltage distribution of memorycells according to an example embodiment of the disclosure.

Referring to FIGS. 2 and 6, the first latch 211 may store first latchinformation Lch1 corresponding to a verifying level Lver. In an exampleembodiment of the disclosure, memory cells having a threshold voltagelevel greater than the verifying level Lver may be inhibiting cells(Inhibiting Cell). The first latch 211 may store ‘1’ as the first latchinformation Lch1. Furthermore, memory cells having a threshold voltagelevel less than the verifying level Lver may be programming cells (PGMCell). The first latch 211 may store ‘0’ as the first latch informationLch1.

The second latch 212 may include second latch information Lch2corresponding to a forcing level Lfc as forcing information for aforcing operation. The forcing level Lfc may be less than the verifyinglevel Lver. In an example embodiment of the disclosure, memory cellshaving a threshold voltage level greater than the forcing level Lfc andless than the verifying level Lver may be forcing cells (Forcing Cell).When the threshold voltage level is greater than the forcing level Lfc,the second latch 212 may store ‘1’ as the second latch information Lch2.Furthermore, if memory cells having a threshold voltage level less thanthe forcing level Lfc are programming cells but not forcing cells, thesecond latch 212 may store ‘0’ as the second latch information Lch2. Thepage buffer 210 may apply a different voltage Vap to each memory cellusing the first and second latch information Lch1 and Lch2.

The page buffer 210 may perform a programming operation including aforcing operation using a two-step verification method. When theprogramming operation is performed with only one voltage level on theprogramming cells, a voltage distribution may widen. Therefore, the pagebuffer 210 of the disclosure may perform, based on the forcing levelLfc, a first program with a programming voltage Vpgm for cells that arenot to be forced and may perform a second program with a forcing voltageVfc for cells to be forced. In more detail, the page buffer 210 mayperform a bit line forcing operation by applying the forcing voltage Vfcto cells to be forced, wherein the forcing voltage Vfc is higher thanthe programming voltage Vpgm and lower than an inhibiting voltage Vinh.

For example, the programming voltage Vpgm may be a ground voltage GND,the inhibiting voltage Vinh may be a power voltage VDD, and the forcingvoltage Vfc may have a voltage level between the power voltage VDD andthe ground voltage GND. Therefore, the page buffer 210 may distinguish acell to be inhibited, a forcing cell, and a programming cell that is notto be forced from one another based on the first and second latchinformation Lch1 and Lch2. In more detail, the page buffer 210 maydistinguish, from each other, a programming cell and an inhibiting cellusing the first latch information Lch1 in a bit line setup operation andmay distinguish, from each other, a forcing cell and a programming cellthat is not to be forced using the second latch information Lch2 in aforcing operation. Accordingly, the page buffer 210 may apply theinhibiting voltage Vinh to the cell to be inhibited, the forcing voltageVfc to the cell to be forced, and the programming voltage Vpgm to theprogramming cell that is not to be forced. Hereinafter, the first latchinformation Lch1 is referred to as bit line setup information and thesecond latch information Lch2 is referred to as forcing information.

FIG. 7 is a flowchart illustrating an operation of a nonvolatile memorydevice according to an example embodiment of the disclosure.

Referring to FIGS. 1 and 7, in operation S10, the control logic 140 mayreceive the programming command CMD from a host and perform aprogramming operation and a verifying operation. The programmingoperation may include an initial programming operation. The controllogic 140 may output a control signal corresponding to the page buffercircuit 110 in correspondence to the programming command CMD. Inoperation S20, the page buffer circuit 110 may determine, using the bitline setup information stored in the first latch 111, whether toprogram/inhibit a bit line. In addition, in operation S30, the pagebuffer circuit 110 may determine, using forcing information stored inthe second latch 112 whether to force a bit line. In operation S40, thepage buffer circuit 110 may distinguish a forcing cell, a programmingcell that is not to be forced, and an inhibiting cell from one anotherbased on the bit line setup information and the forcing information, andmay apply a corresponding voltage to the bit line.

FIG. 8 is a flowchart illustrating an operation of a nonvolatile memorydevice according to an example embodiment of the disclosure.

Referring to FIGS. 2, 6 and 8, in operation S110, the control logic 140may receive the programming command CMD from a host and perform aprogramming operation and a verifying operation. The programmingoperation may include an initial programming operation. In operationS120, the page buffer 210 may determine bit line setup informationincluding programming/inhibiting distinguishing information for cellsusing the verifying level Lver. During a bit line setup process, inoperation S130, the first latch 211 may be connected to the sensing nodeSO through the switching circuit 213 and the bit line setup informationin the first latch 211 may be applied to the sensing node SO. Inoperation S140, the page buffer 210 may determine, according to the bitline setup information, whether a memory cell connected to the pagebuffer 210 is a programming cell. If the memory cell is determined notto be a programming cell in operation S140, in operation S193, the pagebuffer 210 may apply the inhibiting voltage Vinh to a bit line.

If the memory cell is determined to be a programming cell in operationS140, then in operation S150 the first latch 211 and the sensing node SOare disconnected by the switching circuit 213, and in operation S160forcing information may be determined by the forcing level Lfc. Inoperation S170, the second latch 212 may be connected to the sensingnode SO by the switching circuit 213 and forcing information in thesecond latch 212 may be applied to the sensing node SO. In operationS180, the page buffer 210 may determine, according to the forcinginformation, whether the programming cell is a forcing cell. If theprogramming cell is determined not to be a forcing cell in operationS180, in operation S191 the page buffer 210 may apply the programmingvoltage Vpgm to a bit line because a connected memory cell is aprogramming cell that is not to be forced. If the programming cell isdetermined to be a programming cell in operation S180, in operation S192the page buffer 210 may apply the forcing voltage Vfc to a bit line.

Although FIG. 8 shows that the first latch 211 and the sensing node SOare disconnected by the switching circuit 213 in operation S150, theforcing information is determined in operation S160, and the forcinginformation stored in the second latch 212 by the switching circuit 213is applied to the sensing node SO in operation S170, this is only anexample. It should be understood that an order of operation S150, inwhich the first latch 211 and the sensing node SO are disconnected fromeach other, operation S160, in which the forcing information isdetermined, and operation S170, in which the forcing information isapplied to the sensing node SO, may be changed.

FIG. 9 is a circuit diagram of a nonvolatile memory device according toan example embodiment of the disclosure. In more detail, FIG. 9 is anactual circuit diagram according to an example of FIG. 2. In FIG. 9,like reference numerals to those in FIG. 2 denote like elements, andtherefore, repeated descriptions thereof will not be given herein.

Referring to FIG. 9, a page buffer 30 may include a first latch 311, asecond latch 312, a switching circuit 313, a bit line selecting circuit314, and a cell string 320. The first latch 311 may include one or moreinverters. In an example embodiment of the disclosure, the first latch311 may be connected to a separate logic circuit and may receive thepower voltage VDD or the ground voltage GND through the logic circuit.The second latch 312 may also include one or more inverters. In anexample embodiment of the disclosure, the second latch 312 may beconnected to a separate logic circuit and may receive the power voltageVDD or the ground voltage GND through the logic circuit. In anotherexample embodiment of the disclosure, the second latch 312 may receivethe power voltage VDD through a logic circuit.

The switching circuit 313 may include a first latch switch LS1 and asecond latch switch LS2. Although FIG. 9 shows the first and secondlatch switches LS1 and LS2 as transistors, the first and second latchswitches LS1 and LS2 may include any device capable of performing aswitching operation. The first latch switch LS1 may connect the firstlatch 311 to the sensing node SO in response to a setup signal SS. Thesecond latch switch LS2 may connect the second latch 312 to the sensingnode SO in response to a forcing signal SF.

The bit line selecting circuit 314 may include a bit line switch BLTr.The bit line switch BLTr may apply a voltage applied to the sensing nodeSO to the cell string 320 corresponding to a bit line selecting signalSBL. In an example embodiment of the disclosure, the bit line switchBLTr may adjust a voltage applied to the cell string 320 according to avoltage level of the bit line selecting signal SBL. Detaileddescriptions thereof will be described later below with reference toFIG. 10. Although FIG. 9 shows the bit line switch BLTr as a transistor,the bit line switch BLTr may include any device capable of performing aswitching operation. Since the cell string 320 is substantially the sameas the cell string 220 described above with reference to FIG. 2 and thelike, detailed descriptions thereof will not be given herein.

FIG. 10 is a timing diagram of a programming process of a nonvolatilememory device according to an example embodiment of the disclosure. InFIG. 10, like reference numerals to those in FIG. 9 denote likeelements, and therefore, repeated descriptions thereof will not be givenherein.

Referring to FIGS. 9 and 10, during a bit line setup operation (BLSet-up), the setup signal SS applied to a gate of the first latch switchLS1 may transit to logic high and the forcing signal SF applied to agate of the second latch switch LS2 may be maintained at logic low.Thus, the first latch switch LS1 may be changed to an ON state, and thefirst latch 311 and the sensing node SO may be electrically connected toeach other. Furthermore, bit line setup information stored in the firstlatch 311 may be applied to the sensing node SO. The bit line selectingsignal SBL applied to a gate of the bit line switch BLTr may transit toa first voltage level VL1. Accordingly, a bit line switch BLTr may bechanged to an ON state, and the programming voltage Vpgm may be appliedto the cell string 320 according to the bit line setup informationapplied to the sensing node SO.

During a forcing operation (Forcing), the first latch switch LS1 and thebit line switch BLTr may be changed to an OFF state as the setup signalSS and the bit line selecting signal SBL transit to logic low, and thesecond latch switch LS2 may be changed to an ON state as the forcingsignal SF transits to logic high. Accordingly, the second latch 312 andthe sensing node SO may be electrically connected to each other, and theforcing information stored in the second latch 312 may be applied to thesensing node SO. The bit line selecting signal SBL may transit again toa second voltage level VL2. Accordingly, the bit line switch BLTr may bechanged to an ON state, and the forcing voltage Vfc may be applied tothe cell string 320 according to the forcing information applied to thesensing node SO. Since the second voltage level VL2 is lower than thefirst voltage level VL1, the forcing voltage Vfc and the inhibitingvoltage Vinh applied to the cell string 320 may have different voltagelevels.

FIG. 11 is a circuit diagram of a page buffer according to an exampleembodiment of the disclosure. In FIG. 11, like reference numerals tothose in FIG. 9 denote like elements, and therefore, repeateddescriptions thereof will not be given herein.

Referring to FIGS. 9 and 11, the page buffer 30 may include a first pathPath1 connected to the cell string 320 via the first latch 311 and thefirst latch switch LS1 and a second path Path2 connected to the cellstring 320 via the second latch 312 and the second latch switch LS2. Thefirst and second paths Path1 and Path2 may be controlled by theswitching circuit 313. According to an example embodiment of thedisclosure, the first path Path1 may be activated as the first latchswitch LS1 transits to an ON state during the bit line setup operation,and when the bit line setup operation is completed, the first path Path1may be inactivated as the first latch switch LS1 transits to an OFFstate. Next, the second path Path2 may be activated as the second latchswitch LS2 transits to an ON state during the forcing operation.

The bit line setup information stored in the first latch 311 may beapplied to the sensing node SO according to the first path Path1 and thepage buffer 30 may perform a bit line setup operation based on the bitline setup information. The forcing information stored in the secondlatch 312 may be applied to the sensing node SO according to the secondpath Path2 and the page buffer 30 may perform a forcing operation basedon the forcing information.

FIG. 12 is a block diagram of a nonvolatile memory device according toan example embodiment of the disclosure. In FIG. 12, like referencenumerals to those in FIG. 2 denote like elements, and therefore,repeated descriptions thereof will not be given herein.

Referring to FIGS. 2 and 12, a nonvolatile memory device 40 may includea plurality of page buffers 410_1, 410_2, 410_3, and 410_4, and a memorycell array 420. Each of the plurality of page buffers 410_1, 410_2,410_3, and 410_4 A may include a first latch 411, a second latch 412, aswitching circuit 413, and a bit line selecting circuit 414. The pagebuffers 410_2, 410_3, and 410_4, the internal configuration of which isnot shown, may also have the same configuration as the page buffer410_1, the internal configurations of which is shown. The first andsecond latches 411 and 412 and the switching circuit 413 may besubstantially the same as the first and second latches 211 and 212, andthe switching circuit 213 of FIG. 2, respectively. Therefore, detaileddescriptions thereof will not be given herein.

Each of the plurality of page buffers 410_1, 410_2, 410_3, and 410_4 mayhave a shield bit line structure. Each of the plurality of page buffers410_1, 410_2, 410_3, and 410_4 may be connected to a plurality of bitlines at the same time. Although FIG. 12 shows that each of theplurality of page buffers 410_1, 410_2, 410_3, and 410_4 is connected tofour bit lines, this is merely an example. Each of the plurality of pagebuffers 410_1, 410_2, 410_3, and 410_4 may be connected to two or morebit lines. Only one page buffer 410_1 will be described below, but thedisclosure may also be applied to all the other page buffers 410_2,410_3, and 410_4.

The bit line selecting circuit 414 may be connected to a plurality ofbit lines. The plurality of bit lines may include a setup bit line to beprogrammed and a remaining shield bit line not to be programmed. The bitline selecting circuit 414 may set at least one of the plurality of bitlines to be a setup bit line. When a programming operation for the setupbit line is completed, the bit line selecting circuit 414 maysequentially set the next bit line to be the setup bit line and performthe programming operation. When the programming operation for the setupbit line is performed, an inhibiting voltage may be applied to theshield bit line so that an inhibited state may be maintained. As theshield bit line enters the inhibited state, an influence of coupling tothe setup bit line from the other page buffers 410_2, 410_3, and 410_4or neighboring bit lines connected to the other page buffers 410_2,410_3, and 410_4 may be prevented. According to an example embodiment ofthe disclosure, the influence of coupling may be prevented by the shieldbit line even if the setup bit line enters a floating state during theforcing operation. According to another example embodiment of thedisclosure, the page buffer 410_1 may adjust a ratio of the shield bitline to the plurality of bit lines according to a degree of thecoupling. Detailed descriptions thereof will be described later belowwith reference to FIG. 16.

FIG. 13 is a circuit diagram of a nonvolatile memory device according toan example embodiment of the disclosure. In FIG. 13, like referencenumerals to those in FIGS. 9 and 12 denote like elements, and therefore,repeated descriptions thereof will not be given herein.

Referring to FIGS. 9, 12 and 13, a page buffer 50 may include a firstlatch 511, a second latch 512, a switching circuit 513, a bit lineselecting circuit 514, and a bias circuit 515. The first and secondlatches 511 and 512 and the switching circuit 513 may be substantiallythe same as the first and second latches 311 and 312 and the switchingcircuit 313 of FIG. 9, respectively. Therefore, detailed descriptionsthereof will not be given herein.

The bit line selecting circuit 514 may be connected to a plurality ofbit lines. The plurality of bit lines may include a setup bit line to beprogrammed and a remaining shield bit line not to be programmed AlthoughFIG. 13 shows that the bit line selecting circuit 514 is connected tofour bit lines, this is merely an example. The bit line selectingcircuit 514 may be connected to two or more bit lines. Also, althoughnot shown in FIG. 13, each bit line may be connected to a cell string.

The bit line selecting circuit 514 may include switches SeTr, ShTr1,ShTr2, and ShTr3 that are connected to bit lines, respectively. In moredetail, the bit line selecting circuit 514 may include the setup switchSeTr and the shield switches ShTr1, ShTr2, and ShTr3. Although FIG. 13shows the switches SeTr, ShTr1, ShTr2, and ShTr3 as transistors, theswitches SeTr, ShTr1, ShTr2, and ShTr3 may include any device capable ofperforming a switching operation.

Each of the switches SeTr, ShTr1, ShTr2, and ShTr3 may be connected to abit line to control a connection between the sensing node SO and the bitline. The setup switch SeTr may be connected to a setup bit line to beprogrammed and the shield switches ShTr1, ShTr2, and ShTr3 may beconnected to a shield bit line to prevent coupling to the setup bitline. The setup switch SeTr may control voltage application to the setupbit line, in response to a setup selecting signal SSe, so as to performthe bit line setup operation and the forcing operation. Detaileddescriptions of the setup selecting signal SSe and the setup switch SeTrwill be described later below with reference to FIG. 14. The shieldswitches ShTr1, ShTr2, and ShTr3 maintain an OFF state, corresponding toa shield selecting signal SSh, during the bit line setup operation andforcing operation for the setup bit line so that a voltage of thesensing node SO may not be applied to the shield bit line.

The bias circuit 515 may apply a certain voltage to the bit lineaccording to the control of bias signals VSe and VSh. In more detail,the power voltage VDD may be applied to the setup bit line by the setupbias signal VSe, and the power voltage VDD may be applied to the shieldbit line by the shield bias signal VSh. According to an exampleembodiment of the disclosure, while the bit line setup operation for thesetup bit line is performed, the shield bit line may be biased to thepower voltage VDD to maintain an inhibited state. Coupling of the setupbit line may be prevented as the shield bit line is maintained in theinhibited state. FIG. 13 shows that the bias circuit 515 is connected toonly the power voltage VDD. However, in another example embodiment ofthe present disclosure, the bias circuit 515 may be connected to theground voltage GND in addition to the power voltage VDD.

The page buffer 50 may include the first path Path1 connected to thesetup bit line via the first latch 511 and the first latch switch LS1and the second path Path2 connected to the setup bit line via the secondlatch 312 and the second latch switch LS2. The first and second pathsPath1 and Path2 may be controlled by the switching circuit 513.According to an example embodiment of the disclosure, the first pathPath1 may be activated as the first latch switch LS1 transits to an ONstate during the bit line setup operation, and when the bit line setupoperation is completed, the first path Path1 may be inactivated as thefirst latch switch LS1 transits to an OFF state. Next, the second pathPath2 may be activated as the second latch switch LS2 transits to an ONstate during the forcing operation.

FIG. 14 is a timing diagram of a programming process of a nonvolatilememory device according to an example embodiment of the disclosure. InFIG. 14, like reference numerals to those in FIG. 13 denote likeelements, and therefore, repeated descriptions thereof will not be givenherein.

Referring to FIGS. 13 and 14, during a bit line setup operation (BLSet-up), the setup signal SS applied to a gate of the first latch switchLS1 may transit to logic high and the forcing signal SF applied to agate of the second latch switch LS2 may be maintained at logic low.Thus, the first latch switch LS1 may be changed to an ON state, and thefirst latch 511 and the sensing node SO may be electrically connected toeach other. Furthermore, bit line setup information stored in the firstlatch 511 may be applied to the sensing node SO.

The setup selecting signal SSe applied to a gate of the setup switchSeTr may transit to the first voltage level VL1. Accordingly, the setupswitch SeTr may be changed to an ON state, and the programming voltageVpgm may be applied to a cell string connected to the setup bit lineaccording to the bit line setup information applied to the sensing nodeSO. In addition, the setup bias signal VSe may be maintained at logiclow to prevent a bias voltage from being applied to the setup bit line.

As the shield selecting signal SSh applied to a gate of a shield switchShTr is maintained at logic low, the shield switches ShTr1, ShTr2 andShTr3 remain OFF, and the supply voltage VDD may be applied to theshield bit line as the shield bias signal VSh is maintained at logichigh. By this process, the shield bit line may maintain an inhibitedstate.

During a forcing operation (Forcing), the first latch switch LS1 and thesetup switch SeTr may be changed to an OFF state as the setup signal SSand the setup selecting signal SSe transit to logic low, and the secondlatch switch LS2 may be changed to an ON state as the forcing signal SFtransits to logic high. Accordingly, the second latch 512 and thesensing node SO may be electrically connected to each other, and theforcing information stored in the second latch 512 may be applied to thesensing node SO. The setup selecting signal SSe may transit again to thesecond voltage level VL2. Accordingly, the setup switch SeTr may bechanged to an ON state, and the forcing voltage Vfc may be applied tothe cell string connected to the setup bit line according to the forcinginformation applied to the sensing node SO. Since the second voltagelevel VL2 is lower than the first voltage level VL1, the forcing voltageVfc applied to the cell string connected to the setup bit line may havea voltage level different from that of the programming voltage Vpgm.

During the forcing operation, the shield selecting signal SSh may bemaintained at logic low to prevent the forcing voltage Vfc from beingapplied to the shield bit line. In addition, the setup bias signal VSemay also be maintained at logic low to prevent the setup bit line frombeing biased to the power voltage VDD. The shield bias signal VSh ismaintained at logic high so that the shield bit line may maintain aninhibited state. In an example embodiment of the disclosure, differentfrom FIG. 14, the shield bias signal VSh may transit from a forcingoperation to logic low. In the forcing operation, the shield bit linedoes not have to be in an inhibited state. Accordingly, even if theshield bias signal VSh transits to logic low, the setup bit line may notbe affected by coupling.

FIG. 15 is a block diagram of a page buffer according to an exampleembodiment of the disclosure. In FIG. 15, like reference numerals tothose in FIG. 13 denote like elements, and therefore, repeateddescriptions thereof will not be given herein.

Referring to FIGS. 13 and 15, a page buffer 60 may include a first latch611, a second latch 612, a switching circuit 613, a bit line selectingcircuit 614, and a shield bit line decision unit 615. The first andsecond latches 612 and 611, the switching circuit 613, and the bit lineselection circuit 614 may be substantially the same as the first andsecond latches 311 and 312, the switching circuit 313, and the bit lineselecting circuit 314 of FIG. 9, respectively.

The shield bit line decision unit 615 may control the bit line selectingcircuit 614 to adjust a ratio of shield bit lines to all bit lines. If adegree of coupling is high, a relatively large number of shield bitlines may be required to prevent coupling to a setup bit line, and if adegree of coupling is low, a relatively small number of shield bit linesmay be required. The shield bit line decision unit 615 may adjust aratio of the shield selecting signal SSe and the shield selecting signalSSh applied to the bit line selecting circuit 514 according to a degreeof coupling to adjust the ratio of the shield bit line. In more detail,the shield bit line decision unit 615 may increase the ratio of theshield bit line when coupling occurs to a large extent, and may decreasethe shield bit line ratio when coupling occurs to a small extent. In anexample embodiment of the disclosure, the shield bit line decision unit615 may receive information about a degree of coupling and adjust aratio of the shield bit line accordingly.

FIG. 16 is a block diagram of a computing system device including anonvolatile memory device according to an example embodiment of thedisclosure.

Referring to FIG. 16, a computing system device 900 may include amicroprocessor 930 electrically connected to a bus 960, a user interface950, and a nonvolatile memory system 910 having a memory controller 912and a nonvolatile memory device 911. The nonvolatile memory device 911may store data processed/to be processed by the microprocessor 930 viathe memory controller 912. In addition, the nonvolatile memory device911 may also include the nonvolatile memory device described in FIGS. 1through 15. The computing system device 900 may further include a RAM940 and a power supply 920.

If the computing system device 900 is a mobile device, a battery forsupplying an operating voltage of a computing system and a modem such asa baseband chipset may be additionally provided. Furthermore, it will beapparent to those of ordinary skilled in the art that the computingsystem device 900 may be further provided with an application chipset, acamera image processor (CIS), a mobile dynamic random access memory(DRAM), and the like, and thus detailed descriptions thereof will not begiven herein.

Preferably, the memory controller 912 and the nonvolatile memory device911 may include, e.g., a solid-state drive (SSD) using a nonvolatilememory for storing data.

As is traditional in the field, embodiments may be described andillustrated in terms of blocks which carry out a described function orfunctions. These blocks, which may be referred to herein as units ormodules or the like, are physically implemented by analog and/or digitalcircuits such as logic gates, integrated circuits, microprocessors,microcontrollers, memory circuits, passive electronic components, activeelectronic components, optical components, hardwired circuits and thelike, and may optionally be driven by firmware and/or software. Thecircuits may, for example, be embodied in one or more semiconductorchips, or on substrate supports such as printed circuit boards and thelike. The circuits constituting a block may be implemented by dedicatedhardware, or by a processor (e.g., one or more programmedmicroprocessors and associated circuitry), or by a combination ofdedicated hardware to perform some functions of the block and aprocessor to perform other functions of the block. Each block of theembodiments may be physically separated into two or more interacting anddiscrete blocks without departing from the scope of the disclosure.Likewise, the blocks of the embodiments may be physically combined intomore complex blocks without departing from the scope of the disclosure.

While the disclosure has been particularly shown and described withreference to example embodiments thereof, it will be understood thatvarious changes in form and details may be made therein withoutdeparting from the spirit and scope of the following claims.

1. A nonvolatile memory device comprising: a cell string including aplurality of memory cells connected to a bit line; and a page bufferconnected to the bit line via a sensing node and connected to the cellstring via the bit line, wherein: the page buffer includes a first latchthat stores bit line setup information and a second latch that storesforcing information, and the first latch outputs the bit line setupinformation to the sensing node, by being connected to the sensing node,and the second latch outputs the forcing information to the sensing nodeindependently of the first latch by being connected to the sensing node.2. The nonvolatile memory device of claim 1, wherein the second latchdoes not perform a dumping operation for the first latch.
 3. Thenonvolatile memory device of claim 1, wherein: the bit line setupinformation distinguishes between cells to be programmed and cells to beinhibited based on a verifying level, and the forcing informationdistinguishes cells to be forced among the cells to be programmed basedon a forcing level.
 4. The nonvolatile memory device of claim 3, whereinthe page buffer applies: a programming voltage to the cells to beprogrammed, which are not the cells to be forced, based on the bit linesetup information and the forcing information, an inhibiting voltage tothe cells to be inhibited, and a forcing voltage having a voltage levelhigher than a voltage level of the programming voltage and lower than avoltage level of the inhibiting voltage to the cells to be forced. 5.The nonvolatile memory device of claim 1, wherein the page bufferfurther comprises a first switch, which is placed between the firstlatch and the sensing node, that controls a connection between the firstlatch and the sensing node and a second switch, which is placed betweenthe second latch and the sensing node, that controls a connectionbetween the second latch and the sensing node.
 6. The nonvolatile memorydevice of claim 5, wherein: the page buffer performs a bit line setupoperation and a forcing operation during a programming operation for theplurality of memory cells, the first switch connects the first latch tothe sensing node during the bit line setup operation, and the secondswitch connects the second latch to the sensing node during the forcingoperation.
 7. The nonvolatile memory device of claim 6, wherein: thepage buffer performs the forcing operation after completing the bit linesetup operation, the first switch disconnects the first latch from thesensing node when the bit line setup operation is completed, and thesecond switch connects the second latch to the sensing node after thefirst latch and the sensing node are disconnected.
 8. The nonvolatilememory device of claim 1, wherein: the page buffer has a shield bit linestructure connected to a plurality of bit lines, and the plurality ofbit lines comprises a setup bit line to which a bit line setup operationis performed and a shield bit line to which the bit line setup operationis not performed.
 9. The nonvolatile memory device of claim 8, whereinthe shield bit line prevents the setup bit line from being influenced bycoupling of neighboring bit lines while maintaining an inhibited stateduring a forcing operation for the setup bit line.
 10. The nonvolatilememory device of claim 9, wherein the setup bit line connected to cellsto be programmed but not cells to be forced is floated when the forcingoperation is performed.
 11. The nonvolatile memory device of claim 1,wherein: the page buffer performs a programming operation including abit line setup operation and a forcing operation for the memory cells,the first latch outputs the bit line setup information to the sensingnode when performing the bit line setup operation, and the second latchoutputs the forcing information to the sensing node when performing theforcing operation.
 12. A nonvolatile memory device comprises: aplurality of cell strings including a plurality of memory cells; and apage buffer having a shield bit line structure connected to theplurality of cell strings via a plurality of bit lines, wherein the pagebuffer comprises a first path that outputs bit line setup information toa selected memory cell, among the memory cells, and a second path,different from the first path, that outputs forcing information to theselected memory cell, wherein the first and second paths areindependently activated.
 13. The nonvolatile memory device of claim 12,wherein: the page buffer performs a bit line setup operation and aforcing operation during a programming operation for the plurality ofmemory cells, and the page buffer comprises a switching circuit thatactivates the first path during the bit line setup operation andactivates the second path during the forcing operation.
 14. Thenonvolatile memory device of claim 12, wherein: the bit line setupinformation distinguishes between cells to be programmed and cells to beinhibited based on a verifying level, and the forcing informationdistinguishes cells to be forced based on a forcing level.
 15. Thenonvolatile memory device of claim 12, wherein: the plurality of bitlines comprises a setup bit line to which a bit line setup operation isperformed and a shield bit line to which the bit line setup operation isnot performed, and the shield bit line prevents the setup bit line frombeing influenced by coupling of neighboring bit lines while maintainingan inhibited state during a forcing operation for the setup bit line.16. A nonvolatile memory device comprising: a nonvolatile memory havinga plurality of memory-cell strings, each of the memory-cell stringscomprising a plurality of memory cells addressed by a same bit line anda different one of multiple word lines, and the memory cells of each ofthe memory-cell strings addressed by a different bit line than thememory cells of every other of the plurality of memory-cell strings; anda page buffer circuit comprising a first latch, a second latch, and aswitching circuit, wherein the switching circuit conveys first datastored by the first latch and second data stored by the second latch toa selected memory cell of the nonvolatile memory that is addressed by aselected one of the bit lines and a selected one of the word lines,wherein: a first value of the first data indicates the selected memorycell is to be programmed and a second value of the first data indicatesthe selected memory cell is to be inhibited from programming, and afirst value of the second data indicates the selected memory cell is tobe forced and a second value of the second data indicates the selectedmemory cell is not to be forced.
 17. The nonvolatile memory device ofclaim 16, wherein the switching circuit conveys: the first data storedby the first latch to the selected memory cell in response to a firstsignal indicating the selected memory cell has a threshold voltage levelthat is less than a first value, and the second data stored by thesecond latch to the selected memory cell in response to a second signalindicating the selected memory cell has a threshold voltage levelgreater than the first value and less than a second value.
 18. Thenonvolatile memory device of claim 17, wherein the switching circuitcomprises a first switch that is activated by the first signal and asecond switch that is activated by the second signal.
 19. Thenonvolatile memory device of claim 16, further comprising a bit lineselection circuit that conveys the first data or second data, receivedrespectively from the first latch or the second latch, to the selectedbit line in accordance with a bit line selection signal.
 20. Thenonvolatile memory device of claim 16, further comprising a bias circuitthat biases one or more of unselected bit lines with a bias voltage inaccordance with a bias voltage signal.